The present invention relates to a back door device for vehicles such as minivans, and more particularly, to a back door device having a damper stay storage structure for storing a damper stay that urges a back door at the rear end of the vehicle in the opening direction.
For example, Japanese Laid-Open Patent Publications No. 2009-234417 and No. 2003-269039 disclose such back door devices with damper stay storage structures. In the techniques disclosed in the publications, a door opening at the rear end of a vehicle is selectively opened and closed by vertically pivoting a back door.
The technique disclosed in Japanese Laid-Open Patent Publication No. 2009-234417 includes a damper stay at each end of the door opening in the vehicle width direction. Each damper stay is connected to a part of the vehicle body adjacent to the side of the door opening and also connected to the side of the back door to urge the back door in the opening direction. The urging force reduces the operating load on the user when opening the back door. The damper stays are stored in the edges on both sides of the door opening in the vehicle width direction.
Japanese Laid-Open Patent Publication No. 2003-269039 discloses a technique in which a hinge arm, which extends from the vehicle interior, is connected to the back door. The proximal end of the hinge arm is coupled to a damper stay and a slide member, which are stored in the vehicle roof, via separate shaft members. The damper stay urges the back door in the opening direction via the hinge arm. The slide member is driven by a motor to reciprocate. As the slide member reciprocates, the hinge arm pivots, which allows the back door to pivot upward while being assisted by the urging force of the damper stay.
Since the technique of Japanese Laid-Open Patent Publication No. 2009-234417 requires a damper stay storage space on each side of the door opening in the vehicle width direction, the width of the door opening is narrowed accordingly. In the technique of Japanese Laid-Open Patent Publication No. 2003-269039, the damper stay is stored in the vehicle roof, allowing the width of the door opening to be increased. Nevertheless, the link members such as the hinge arm between the damper stay and the back door complicates the connecting structure of the damper stay. Also, the damper stay and other components, which are stored in the vehicle roof, cause the roof panel facing the passenger compartment to bulge inward, narrowing the field of rearward view.